The possibility of neutron or proton singlet pairing and superfluidity in neutron star matter is investigated, and the energy gap and corresponding critical temperature is calculated or estimated as a function of Fermi momentum or density. The calculations are performed for three different potentials:
a "one-pion-exchange gaussian" (OPEC) potential, an "effective" OPEC potential, and an effective Reid soft-core potential obtained by a method of "lowest-order constrained variation".
The results indicate that neutron superfluidity, corresponding specifically to '&-state pairing, may exist in a low-density shell in the nuclear-matter region in neutron stars, i.e. for densities 4.6 x IO" g/cm3 < p < 1.6 x lOI g/cm3, and the maximum self-consistent energy gap is A( k;) = 2-5 MeV for a neutron Fermi momentum k;= 0.7-l .O fm-'. Superfluidity or superconductivity corresponding to '$,-state pairing for the proton subsystem is quite likely at higher densities, i.e. for 2.4 x lOI g/cm3 < p (7.8 x lOI g/cm3, and the maximum energy gap for the OPEC potential is A( kfL) f 0.3-0.6 MeV for a proton Fermi momentum kF 5 0.7 fm-'. The estimated critical temperatures seem to be higher than expected temperatures inside neutron stars.